The Last Apprentice by Joseph Delaney

First published in Great Britain in 2006 by The Bodley Head under the title : The Spook's secret. Accelerated Reader AR MG 5.5 13.0 118249.

For years, Old Gregory has been the Spook for the county, ridding the local villages of evil. Now his time is coming to an end, but who will take over for him? Twenty-nine apprentices have tried--some floundered, some fled, some failed to stay alive. Only Thomas Ward is left. He's the last hope--the last apprentice.